Document FR-2,692,320 describes a pumping device for viscous fluids, comprising injection of a fluidifying product upstream from the pump inlet. This device notably has the drawback of requiring an additional operation of setting a special line for injection of the product.
Document FR-2,727,475 describes a pumping device driven by a continuous tube wound from the surface, said tube allowing an additive to be injected downstream from the pump discharge end. However, the fluid at the pump inlet is not in contact with the additive and keeps such a high viscosity that the pumping efficiency can be affected thereby.